Overhead scanner, image obtaining method, and computer-readable recording medium

ABSTRACT

An overhead scanner successively obtains a plurality of images by controlling an area sensor, calculates a movement pattern by image difference extraction by using the obtained images, detects a page turning movement on the basis of the movement pattern, and determines that a read operation be started when the page turning movement is detected.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-039520, filed Feb. 28, 2013, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an overhead scanner, an image obtainingmethod, and a computer-readable recording medium.

2. Description of the Related Art

Conventional overhead scanners that improve operability have beendeveloped.

In order to provide excellent operability when reading documents and toobtain high-definition images, there is an overhead scanner thatdetermines that a read operation is started on the basis of velocityvectors obtained by extracting feature points (see Japanese PatentApplication Laid-open No. 2011-254366).

Moreover, there is a scanner that, when a scanned image is formed bycorrecting a frame of a moving image captured by a high-speed areasensor, successively monitors a projected light pattern reflected froman object, detects a change within an area region by extracting adifference, and detects a change in an object by comparing the detectionresults (see Japanese Patent Application Laid-open No. 2003-244531).

However, there is a problem with conventional scanners that they easilyproduce a false detection, i.e., the detection of a movement other thana predetermined movement, and therefore the accuracy with which apredetermined movement is correctly detected is low.

The present invention is achieved in view of the above and has an objectto provide an overhead scanner, an image obtaining method, and acomputer-readable recording medium capable of preventing a falsedetection and detecting the start of a read operation with highaccuracy.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an overhead scannerincludes an area sensor; and a control unit, wherein the control unitincludes an area-image obtaining unit that successively obtains aplurality of images by controlling the area sensor, a movement-patterncalculating unit that calculates a movement pattern by image differenceextraction by using the images obtained by the area-image obtainingunit, a movement detecting unit that detects a page turning movement ona basis of the movement pattern calculated by the movement-patterncalculating unit, and a read-start determining unit that determines thata read operation be started when the page turning movement is detectedby the movement detecting unit.

According to another aspect of the present invention, an image obtainingmethod includes an area-image obtaining step of successively obtaining aplurality of images by controlling an area sensor; a movement-patterncalculating step of calculating a movement pattern by image differenceextraction by using the images obtained in the area-image obtainingstep; a movement detecting step of detecting a page turning movement ona basis of the movement pattern calculated in the movement-patterncalculating step; and a read-start determining step of determining thata read operation be started when the page turning movement is detectedin the movement detecting step, wherein the area-image obtaining step,the movement-pattern calculating step, the movement detecting step, andthe read-start determining step are executed by a control unit of anoverhead scanner that includes the area sensor and the control unit.

According to still another aspect of the present invention, anon-transitory computer-readable recording medium that stores therein aprogram that causes a control unit of an overhead scanner including anarea sensor and the control unit to execute: an area-image obtainingstep of successively obtaining a plurality of images by controlling thearea sensor; a movement-pattern calculating step of calculating amovement pattern by image difference extraction by using the imagesobtained in the area-image obtaining step; a movement detecting step ofdetecting a page turning movement on a basis of the movement patterncalculated in the movement-pattern calculating step; and a read-startdetermining step of determining that a read operation be started whenthe page turning movement is detected in the movement detecting step.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a hardware configuration diagram illustrating an example of anoverhead scanner;

FIG. 2 is a block diagram illustrating an example of a storage unit ofthe overhead scanner;

FIG. 3 illustrates an example of the appearance of the apparatus inwhich a linear imaging unit and an area imaging unit are integrated andis a diagram illustrating the relationship between the main-scanningdirection, the sub-scanning direction, and the rotation directioncontrolled by a motor;

FIG. 4 is a functional block diagram illustrating an example of acontrol unit of the overhead scanner;

FIG. 5 illustrates a state where the linear imaging unit is viewed fromthe side thereof and is a diagram illustrating an example of lightemitted from a line light source controlled by a light-source controlunit.

FIG. 6 is a flowchart illustrating an example of the basic processperformed by the overhead scanner in the present embodiment;

FIG. 7 is a flowchart illustrating an example of the embodying processperformed by the overhead scanner in the present embodiment;

FIG. 8 is a flowchart representing a subroutine of a movement-patternmonitoring process;

FIG. 9 is a diagram schematically illustrating a method of comparing thegradation at each pixel of an image of the current frame (N) and animage of the last frame (N−1);

FIG. 10 is a diagram schematically illustrating changed blocks among theblocks (18×6) obtained by dividing an image region horizontally into 18blocks and vertically into 6 blocks;

FIG. 11 is a diagram illustrating an example of changed blocks detectedwhen a page turning movement is performed;

FIG. 12 is a diagram schematically illustrating a changed block amongthe blocks (3×1) obtained by dividing an image region horizontally intothree blocks and vertically into one block;

FIG. 13 is a diagram schematically illustrating changed blocks among theblocks (20×20) obtained by dividing an image region horizontally into 20blocks and vertically into 20 blocks;

FIG. 14 is a diagram illustrating an example of a division in the casewhere an image region is divided into smaller blocks in both endportions and into larger blocks in the central portion;

FIG. 15 is a diagram illustrating an example of a division where animage region is divided into blocks such that a movement can be easilymonitored at specific points;

FIG. 16 is a diagram illustrating a determination result of changedblocks in a difference image of the current frame (N);

FIG. 17 is a diagram illustrating a determination result of changedblocks in a difference image of the next frame (N+1);

FIG. 18 is a diagram illustrating a determination result of changedblocks in a difference image of the second frame (N+2) after the currentframe;

FIG. 19 is a flowchart representing a subroutine of a false-detectionexclusion process;

FIG. 20 is a diagram illustrating an example of a detection of changedblocks in (1) a case where a movement is detected in all regions;

FIG. 21 is a diagram illustrating an example of the detection of changedblocks in (2) a case where a specific region did not move;

FIG. 22 is a diagram illustrating an example of the detection of changedblocks in (3) a case where a movement is detected at a point that doesnot move during a page turning movement;

FIG. 23 is a flowchart representing a subroutine of a hand-removalmonitoring process; and

FIG. 24 is a diagram schematically illustrating an example of anextracted image when a hand remains in place.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of an overhead scanner, an image obtaining method,and a computer-readable recording medium according to the presentinvention will be explained below in detail with reference to theaccompanying drawings. The present invention is not limited to theembodiments. Specially, although a document of a book or the like issometimes described as an object to be read in the present embodiment,the present invention is not to be thus limited, but a stapled medium, astack of single-cut sheets, and the like may be used as an object to beread.

1. Configuration of Present Embodiment

The configuration of an overhead scanner 100 according to the presentembodiment will be explained with reference to FIG. 1. FIG. 1 is ahardware configuration diagram illustrating an example of the overheadscanner 100.

As illustrated in FIG. 1, the overhead scanner 100 includes at least alinear imaging unit 110, an area imaging unit 120, and a control unit102. In the present embodiment, the overhead scanner 100 furtherincludes a storage unit 106, an input/output interface unit 108, aninfrared light source 130, and a line light source 140. These units arecommunicatively connected to one another via an arbitrary communicationchannel.

The storage unit 106 stores therein various databases, tables, files,and the like. The storage unit 106 is a storage unit. For example, amemory device, such as a RAM and a ROM, a fixed disk drive, such as ahard disk, a flexible disk, an optical disk, or the like can be used asthe storage unit 106. The storage unit 106 records therein computerprograms for providing instructions to a CPU (Central Processing Unit)and executing various processes. FIG. 2 is a block diagram illustratingan example of the storage unit 106 of the overhead scanner 100.

As illustrated in FIG. 2, the storage unit 106 includes an image-datatemporary file 106 a, a processed-image data file 106 b, and anindicator file 106 c.

Among them, the image-data temporary file 106 a temporarily storestherein image data read by the linear imaging unit 110 or the areaimaging unit 120.

The processed-image data file 106 b stores therein processed or editedimage data from image data read by the linear imaging unit 110.

The indicator file 106 c is an indicator storage unit that storestherein color, shape, and the like of an indicator, such as a hand and afinger, provided by a user. The indicator file 106 c may store thereincolor (skin color), shape, and the like of a users' hand or finger foreach user.

The input/output interface unit 108 connects the linear imaging unit110, the area imaging unit 120, the infrared light source 130, and theline light source 140 to the control unit 102. A halogen light sourcecan be used as the infrared light source 130. The line light source 140may be an LED light source, a laser light source, or the like, and itemits light onto the area to be read.

The linear imaging unit 110 scans a document placed face-up from abovein order to read an image on the document by using a linear sensor 13.In the present embodiment, as illustrated in FIG. 1, the linear imagingunit 110 includes a controller 11, a motor 12, the linear sensor (linesensor) 13, and an A/D converter 14. The controller 11 controls themotor 12, the linear sensor 13, and the A/D converter 14 in accordancewith instructions from the control unit 102 via the input/outputinterface unit 108. The linear sensor 13 photoelectrically convertslight that reaches it from a line in the main-scanning direction of adocument into an analog charge quantity for each pixel on the line.Then, the A/D converter 14 converts the analog charge quantity outputfrom the linear sensor 13 into a digital signal and outputsone-dimensional image data. When the motor 12 is driven to rotate, adocument line targeted for reading by the linear sensor 13 shifts in thesub-scanning direction. Accordingly, one-dimensional image data for eachline is output from the A/D converter 14 and the control unit 102generates two-dimensional image data by combining a plurality of piecesof one-dimensional image data. FIG. 3 illustrates an example of theappearance of the apparatus in which the linear imaging unit 110 and thearea imaging unit 120 are integrated and is a diagram illustrating therelationship between the main-scanning direction, the sub-scanningdirection, and the rotation direction controlled by the motor 12.

As illustrated in FIG. 3, when a document is placed face-up and isimaged from above by the linear imaging unit 110, one-dimensional imagedata of a line in the main-scanning direction illustrated in FIG. 3 isread by the linear sensor 13. Then, when the linear sensor 13 is causedto rotate in the rotation direction in FIG. 3 by driving the motor 12,the line to be read by the linear sensor 13 shifts in the sub-scanningdirection in FIG. 3 in accordance with the rotation. Accordingly,two-dimensional image data of the document is read by the linear imagingunit 110.

Here, the description refers back to FIG. 1. The area imaging unit 120scans a document placed face-up from above in order to read an image onthe document by using an area sensor 22. In the present embodiment, asillustrated in FIG. 1, the area imaging unit 120 includes a controller21, the area sensor 22, and an A/D converter 23. The controller 21controls the area sensor 22 and the A/D converter 23 in accordance withinstructions from the control unit 102 via the input/output interfaceunit 108. The area sensor 22 photoelectrically converts light thatreaches it from the document face (which is a two-dimensional plane withone dimension in the main-scanning direction and the other in thesub-scanning direction illustrated in FIG. 3) into an analog chargequantity for each pixel. Then, the A/D converter 23 converts the analogcharge quantity output from the area sensor 22 into a digital signal andoutputs two-dimensional image data. Accordingly, two-dimensional imagedata is output from the A/D converter 23. In the present embodiment,because the linear sensor 13 can read a large number of pixels in oneline compared with the area sensor 22, an image read by the linearimaging unit 110 has higher definition (higher resolution) than an imageread by the area imaging unit 120. Hereinafter, in order to distinguishbetween them, in some cases, an image read by the area imaging unit 120is referred to as an “area image” and an image read by the linearimaging unit 110 is referred to as a “linear image”.

The control unit 102 consists of a CPU or the like that performs overallcontrol of the overhead scanner 100. The control unit 102 includes aninternal memory for storing a control program, programs defining variousprocessing procedures and the like, and required data. The control unit102 performs information processing for executing various processes inaccordance with these programs. FIG. 4 is a functional block diagramillustrating an example of the control unit 102 of the overhead scanner100.

As illustrated in FIG. 4, the control unit 102 roughly includes anarea-image obtaining unit 102 a, a movement-pattern calculating unit 102b, a movement detecting unit 102 c, a read-start determining unit 102 d,a linear-image obtaining unit 102 e, and a light-source control unit 102f.

The area-image obtaining unit 102 a successively obtains a plurality ofarea images by controlling the area imaging unit 120. For example, asdescribed above, the area-image obtaining unit 102 a repeats a processof obtaining image data by the area sensor 22 performing photoelectricalconversion and the A/D converter 23 performing A/D conversion bycontrolling the controller 21 of the area imaging unit 120 and thenstoring the image data in an image-data temporary file (buffer) 106 a.In other words, the area-image obtaining unit 102 a has a function ofmonitoring document page turning, the movement of a user's hand, and thelike by capturing motions with the area sensor 22 and obtainingsuccessive images (moving image). In the present embodiment, thearea-image obtaining unit 102 a can obtain infrared images by infraredirradiation from the infrared light source 130.

The movement-pattern calculating unit 102 b calculates a movementpattern by performing image difference extraction by using a pluralityof images obtained by the area-image obtaining unit 102 a. Specifically,the movement-pattern calculating unit 102 b performs image differenceextraction by using the image data of a plurality of area images thatare stored in the image-data temporary file 106 a by the area-imageobtaining unit 102 a. For example, the movement-pattern calculating unit102 b extracts a region where there is a difference between the last(time t−1) area image, which is obtained and stored in the image-datatemporary file 106 a by the area-image obtaining unit 102 a, and a newlyobtained current (time t) area image. The movement-pattern calculatingunit 102 b may calculate a movement pattern by a well-known imagedifference extraction method. The movement-pattern calculating unit 102b may calculate a movement pattern by dividing an image region into apredetermined number of blocks. When an image region is divided into anarbitrary number of blocks, if the number of changed pixels in one blockis equal to or greater than a predetermined number, the movement-patterncalculating unit 102 b may evaluate the block as a changed block. Themovement-pattern calculating unit 102 b may divide an image region intoan arbitrary number of blocks and, for example, the movement-patterncalculating unit 102 b may divide an image region corresponding to theinitial movement of a page turning movement into smaller blocks. Theimage difference extraction method in the present embodiment will bedescribed in detail later with reference to the drawings.

The movement detecting unit 102 c detects a page turning movement on thebasis of a movement pattern calculated by the movement-patterncalculating unit 102 b. The movement detecting unit 102 c may screen outfalse-positive patterns other than a page turning movement and excludethe detection. As an example, if a movement pattern corresponds to atleast one of (1) a case where a movement is detected in all regions, (2)a case where a specific region did not move, and (3) a case where amovement is detected at a point that does not move during a page turningmovement, the movement detecting unit 102 c may exclude the detection asa false-positive pattern.

The movement detecting unit 102 c may divide an image regioncorresponding to the initial movement of a page turning movement intosmaller blocks, and, when a block corresponding to the initial movementof a page turning movement changes, the movement detecting unit 102 cmay determine that a page turning movement has been performed.

When a page turning movement is detected by the movement detecting unit102 c, the read-start determining unit 102 d determines that a readoperation be started. The read-start determining unit 102 d maydetermine that a read operation be started on the condition that themovement based on the movement pattern calculated by performing imagedifference extraction by the movement-pattern calculating unit 102 b hasstopped. The read-start determining unit 102 d may manage the powersupply of the linear sensor 13 to save power. For example, when theread-start determining unit 102 d determines that a read operation bythe linear sensor 13 be started, the read-start determining unit 102 dmay activate the circuit of the linear sensor 13, and, when theread-start determining unit 102 d does not determine that a readoperation by the linear sensor 13 be started, the read-start determiningunit 102 d may stop the circuit of the linear sensor 13.

When the read-start determining unit 102 d determines that a readoperation be started, the linear-image obtaining unit 102 e obtainslinear images from the linear sensor 13 by controlling the linearimaging unit 110. For example, as described above, the linear-imageobtaining unit 102 e drives the motor 12 to rotate by controlling thecontroller 11 of the linear imaging unit 110, generates two-dimensionalimage data (image data of linear images) by combining a plurality ofpieces of one-dimensional image data on lines, which are obtained by thelinear sensor 13 performing photoelectric conversion and the A/Dconverter 14 performing A/D conversion, and stores the two-dimensionalimage data in the image-data temporary file 106 a.

The light-source control unit 102 f controls the infrared light source130 such that it emits light indicating a controllable state of thelinear sensor 13 or controls the line light source 140 such that itemits light indicating a reading range of the linear sensor 13. FIG. 5illustrates a state where the linear imaging unit 110 is viewed from theside thereof and is a diagram illustrating an example of light emittedfrom the line light source 140 controlled by the light-source controlunit 102 f. As illustrated in FIG. 5, the light-source control unit 102f may rotate the line light source 140 in the rotation direction bydriving the motor 12 and thus move the line light that is emitted fromthe line light source 140 and extends in the main-scanning direction inthe sub-scanning direction within the reading range, thereby notifyingthe user of the reading range.

2. Processing in Present Embodiment

An explanation will be given of an example of the processing performedby the overhead scanner 100 having the above configuration withreference to FIG. 6 to FIG. 24.

[2-1. Basic Process]

An explanation will be given of an example of the basic processperformed by the overhead scanner 100 in the present embodiment withreference to FIG. 6. FIG. 6 is a flowchart illustrating an example ofthe basic process performed by the overhead scanner 100 in the presentembodiment.

As illustrated in FIG. 6, first, the area-image obtaining unit 102 asuccessively obtains a plurality of area images by controlling the areaimaging unit 120 (Step SA-1). For example, the area-image obtaining unit102 a continuously performs a process of obtaining image data of an areaimage by the area sensor 22 performing photoelectric conversion and theA/D converter 23 performing A/D conversion by controlling the controller21 of the area imaging unit 120 and storing the image data in theimage-data temporary file 106 a. The area-image obtaining unit 102 a mayobtain infrared images by infrared irradiation. Accordingly, it ispossible to accurately monitor a document page turning movement, themovement of a user's hand, and the like.

Then, the movement-pattern calculating unit 102 b calculates a movementpattern by image difference extraction by using the images obtained bythe area-image obtaining unit 102 a (Step SA-2). Specifically, themovement-pattern calculating unit 102 b performs image differenceextraction by using the image data of the area images that are stored inthe image-data temporary file 106 a by the area-image obtaining unit 102a. For example, the movement-pattern calculating unit 102 b extracts thegradation difference at each pixel between the last (time t−1) areaimage, which is obtained and stored in the image-data temporary file 106a by the area-image obtaining unit 102 a, and a newly obtained current(time t) area image. The movement-pattern calculating unit 102 b maycalculate a movement pattern by calculating a gradation difference inunits of blocks obtained by dividing an image region into apredetermined number of blocks instead of a gradation difference inunits of pixels. When the number of changed pixels in one block is equalto or greater than a predetermined number, the movement-patterncalculating unit 102 b may evaluate the block as a changed block.Alternatively, when the gradation difference value in one block is equalto or greater than a predetermined value, the movement-patterncalculating unit 102 b may evaluate the block as a changed block. Themovement-pattern calculating unit 102 b may divide an image region intoan arbitrary number of blocks or blocks having an arbitrary shape. Forexample, the movement-pattern calculating unit 102 b may divide an imageregion corresponding to the initial movement of a page turning movementinto smaller blocks. It is possible to arbitrarily set the time intervalat which two images are obtained for which a difference is calculated.

Then, the movement detecting unit 102 c detects a page turning movementon the basis of the movement pattern calculated by the movement-patterncalculating unit 102 b (Step SA-3). For example, when a changed blocktransitions from left to right, the movement detecting unit 102 c maydetect the movement pattern as a page turning movement. Moreover, when ablock corresponding to the initial movement of a page turning movementchanges, the movement detecting unit 102 c may determine that a pageturning movement has been performed. The movement detecting unit 102 cmay screen out false-positive patterns other than a page turningmovement and exclude the detection. As an example, if a movement patterncorresponds to at least one of (1) a case where a movement is detectedin all regions, (2) a case where a specific region did not move, and (3)a case where a movement is detected at a point that does not move duringa page turning movement, the movement detecting unit 102 c may excludethe detection as a false-positive pattern.

When a page turning movement is not detected by the movement detectingunit 102 c (No in Step SA-4), the read-start determining unit 102 dreturns the process to Step SA-1 and continues to monitor for a documentpage turning movement, the movement of a user's hand, and the like.

In contrast, when a page turning movement is detected by the movementdetecting unit 102 c (Yes in Step SA-4), the read-start determining unit102 d determines that a read operation by the linear sensor 13 bestarted and the linear-image obtaining unit 102 e obtains linear imagesfrom the linear sensor 13 by controlling the linear imaging unit 110(Step SA-5). The read-start determining unit 102 d may determine that aread operation be started on the condition that the movement based onthe movement pattern calculated by performing image differenceextraction by the movement-pattern calculating unit 102 b has stopped.In other words, even if it is determined that a page turning movement isbeing performed, the read-start determining unit 102 d may be kept onstandby for the start of a read operation until the page turningmovement ends or the movement of a user's hand stops. When theread-start determining unit 102 d determines that a read operation bestarted, the linear-image obtaining unit 102 e obtains linear imagesfrom the linear sensor 13 by controlling the linear imaging unit 110.For example, the linear-image obtaining unit 102 e drives the motor 12to rotate by controlling the controller 11 of the linear imaging unit110, generates two-dimensional image data by combining a plurality ofpieces of one-dimensional image data on lines, which are obtained by thelinear sensor 13 performing photoelectric conversion and the A/Dconverter 14 performing A/D conversion, and stores the two-dimensionalimage data in the image-data temporary file 106 a. When the aboveprocess ends, in order to handle a new page turning movement, thecontrol unit 102 may return the process to Step SA-1, repeat theprocesses in Step SA-1 to Step SA-4 described above, and continue tomonitor document page turning, the movement of a user's hand, and thelike.

The above is an example of the basic process performed by the overheadscanner 100 in the present embodiment.

[2-2. Embodying Process]

Next, an explanation will be further given of an example of theembodying process in the basic process described above with reference toFIG. 7 to FIG. 24. The embodying process further includes afalse-detection exclusion process, a hand-removal monitoring process, animage correction process, and the like. FIG. 7 is a flowchartillustrating an example of the embodying process performed by theoverhead scanner 100 in the present embodiment.

As illustrated in FIG. 7, first, the control unit 102 of the overheadscanner 100 performs a movement-pattern monitoring process bycontrolling the area imaging unit 120 (Step SB-1). FIG. 8 is a flowchartrepresenting a subroutine of a movement-pattern monitoring process.

As illustrated in FIG. 8, the area-image obtaining unit 102 a obtainsimage data of infrared images by controlling the area imaging unit 120(Step SC-1).

Then, the movement-pattern calculating unit 102 b compares the obtainedarea image (N) with the image of the last frame (N−1) in order toextract the gradation difference at each pixel (Step SC-2). FIG. 9 is adiagram schematically illustrating a method of comparing the gradationat each pixel of the image of the current frame (N) and the image of thelast frame (N−1).

As illustrated in FIG. 9, the movement-pattern calculating unit 102 bcompares the gradation value of the pixels (for example, A and A′indicated by broken-line rectangles in FIG. 9) at the same coordinatesfor the image of the current frame (N) and the image of the last frame(N−1). The movement-pattern calculating unit 102 b compares thegradation of the target pixel A and that of the target pixel A′ of thelast frame. If the gradation difference |A-A′| is equal to or largerthan a fixed value, the movement-pattern calculating unit 102 bdetermines that the pixel has changed and marks the pixel A. Themovement-pattern calculating unit 102 b repeatedly performs this processin a similar manner on a pixel B and subsequent pixels, and finallymarked portions represent the extracted difference.

Here, the description refers back to FIG. 8. The movement-patterncalculating unit 102 b divides the extracted difference image intoblocks and extracts changed block images (N′) that are changed blocks(Step SC-3). For example, the movement-pattern calculating unit 102 bmay divide an area image into 1 to 20 blocks both vertically andhorizontally and may evaluate how many changed pixels are present ineach block. FIG. 10 is a diagram schematically illustrating changedblocks among the blocks (18×6) obtained by dividing an image regionhorizontally into 18 blocks and vertically into 6 blocks.

As illustrated in FIG. 10, when the number of changed pixels (the numberof marked pixels) obtained in Step SC-2 is equal to or greater than afixed value in a divided block, the movement-pattern calculating unit102 b marks the block as a changed block. In the example in FIG. 10,because the number of changed pixels is equal to or greater than a fixedvalue in the three upper-left blocks, these blocks are marked (blackrectangles) as changed blocks. FIG. 11 is a diagram illustrating anexample of changed blocks detected when a page turning movement isperformed. In FIG. 11, the changed blocks are marked by hatching.

As illustrated in FIG. 11, when a page turning movement is performed,the edge of the moved page, the characters in the page, and the likeappear as a change in the gradation value in the area image; therefore,the movement-pattern calculating unit 102 b can detect a block in whichthe number of changed pixels is equal to or greater than a fixed valueas a changed block. Accordingly, the movement of the edge of a page andthe movement of the content, such as characters, in a page can bedetected as an image difference. The number and shape of divided blockscan be arbitrarily set as described below. FIG. 12 is a diagramschematically illustrating a changed block among the blocks (3×1)obtained by dividing an image region horizontally into three blocks andvertically into one block.

As illustrated in FIG. 12, when the number of changed pixels obtained inStep SC-2 is equal to or greater than a fixed value in a divided block,the movement-pattern calculating unit 102 b marks the block as a changedblock. In the example in FIG. 12, because the number of changed pixelsis equal to or greater than a fixed value in the left block, the blockis marked (black rectangle) as a changed block. As an example, when thechanged block transitions from the right block to the central block tothe left block, the movement detecting unit 102 c, which will bedescribed later, may determine that a page turning movement has beenperformed in a direction from right to left. In a similar manner, whenthe changed block transitions from the left block to the central blockto the right block, the movement detecting unit 102 c may determine thata page turning movement has been performed in a direction from left toright. In this manner, when the number of blocks is three, it ispossible to detect a pattern of a minimum movement of turning a page ofa book. Another example of the number of divided blocks is given in FIG.13, which is a diagram schematically illustrating changed blocks amongthe blocks (20×20) obtained by dividing an image region horizontallyinto 20 blocks and vertically into 20 blocks.

As illustrated in FIG. 13, if the number of changed pixels obtained inStep SC-2 is equal to or greater than a fixed value in a divided block,the movement-pattern calculating unit 102 b marks the block as a changedblock. In the example in FIG. 13, in the block group on the left siderelative to the center and the upper-left block group, the number ofchanged pixels in some blocks is equal to or greater than a fixed value;therefore, the movement-pattern calculating unit 102 b marks these blockas changed blocks. In this manner, it is possible to evaluate the changeof the whole area image region more finely by dividing the area imageregion into smaller blocks. In other words, it is possible to detect asmall change in the gradation of a medium such as a book. Therefore, itis possible to improve the accuracy of excluding false detections by amatching process. In contrast, as illustrated in FIG. 12, if the numberof divided blocks is reduced, the processing load decreases; however,only a rough change can be detected, which increases the possibility ofa false detection. Thus, the block division method (density of dividedblocks and the like) can be determined in accordance with the trade-offbetween the processing speed and the detection accuracy. If the numberof divided blocks is maximized, the number of blocks becomes equal tothe number of pixels in an area image. Therefore, in the presentembodiment, the explanation of the process in the case where blockdivision is performed can be applied also to the process in the casewhere block division is not performed.

Next, another embodiment of the distribution of the number of dividedblocks and the shape of the divided blocks will be described below. FIG.14 is a diagram illustrating an example of a division in the case wherean image region is divided into smaller blocks in both end portions andinto larger blocks in the central portion.

As illustrated in FIG. 14, in order to detect more change information onthe initial movement of a page turning movement, which tends torepresent the characteristics of a page turning movement, such as themovement of holding a page by hand and the movement of the edge of apage, the number of blocks in both end portions in an area image regionmay be increased by setting the number of divisions to be large in bothend portions. In contrast, as in the portion near the center in FIG. 14,the number of divisions is reduced in the central portion in which it issatisfactory to detect only a movement that a page passes over thecentral portion (i.e., change information does not need to be large);therefore, it is possible to satisfy both the processing speed and thedetection accuracy. FIG. 15 is a diagram illustrating an example of adivision where an image region is divided into blocks such that amovement can be easily monitored at specific points.

A page turning movement may be detected in the following manner.Specifically, as illustrated in FIG. 15, monitoring points illustratedas <1> to <5> in FIG. 15 are set and the movement-pattern calculatingunit 102 b detects changed blocks. If the movement detecting unit 102 cdetects that the changed blocks transition in the order of <1> to <2> to<3> to <4> to <5>, the movement detecting unit 102 c may detect themovement pattern as a page turning movement. By setting the monitoringpoints in such a manner, when a specific hand motion (gesture) is madeor a hand moves in an area image region, scanning can be started.

Here, the description refers back to FIG. 8. The movement detecting unit102 c determines whether a page turning movement is performed on thebasis of the changed blocks detected in Step SC-3 described above (StepSC-4). More specifically, the movement detecting unit 102 c evaluatesthe transition of the changed blocks between successive frames anddetermines whether a movement pattern matches a specific movementpattern. An explanation will be given of an example (transition example)of the transition of a movement pattern targeted for detecting a pageturning movement with reference to FIG. 16 to FIG. 18. FIG. 16 is adiagram illustrating a determination result of changed blocks in adifference image of the current frame (N). FIG. 17 is a diagramillustrating a determination result of changed blocks in a differenceimage of the next frame (N+1). FIG. 18 is a diagram illustrating adetermination result of changed blocks in a difference image of thesecond frame (N+2) after the current frame. In the drawings, portionsmarked by black rectangles represent changed blocks.

As in the example in the drawings, when the Left area, the Center area,and the Right area are set in an image divided into blocks, the movementdetecting unit 102 c determines whether a movement pattern (that is, atransition pattern of changed blocks) of the successive block images isa specific movement pattern corresponding to a page turning movement.For example, as illustrated in FIG. 16 to FIG. 18, when the changedblocks transition in the order of the Left area to the Center area tothe Right area, the movement detecting unit 102 c may determine that apage turning movement is performed in a direction from left to right.Although not illustrated, in a similar manner, when the changed blockstransition in the order of the Right area to the Center area to the Leftarea, the movement detecting unit 102 c may determine that a pageturning movement is performed in a direction from right to left. Byperforming this movement detecting process, it is possible to detect theflow of a series of movements. The series of movements includes “(1)holding a page (detection of the movement of the edge), (2) turning apage (detection of the movement of passing over the center of an image),and (3) releasing a page (detection of the movement of the oppositeedge)”, which are the most common characteristics of a page turningmovement.

Here, the description refers back to FIG. 8. When the movement detectingunit 102 c does not determine that a page turning movement has beenperformed (No in Step SC-4), the movement detecting unit 102 c returnsthe process to Step SC-1 and repeats the processes in Steps SC-1 to SC-4described above.

In contrast, when the movement detecting unit 102 c detects a pageturning movement (Yes in Step SC-4), if the condition to stop the startof a read operation is not satisfied, the read-start determining unit102 d determines that a read operation be started and the linear-imageobtaining unit 102 e obtains linear images (Step SC-5).

Even if the movement detecting unit 102 c determines that a movementpattern is a specific movement pattern corresponding to a page turningmovement, it is possible that a different movement may be accidentallydetermined as a movement that is the same as a page turning movement.Therefore, in order to screen out false-positive patterns other than apage turning movement and exclude the detection, the movement detectingunit 102 c may additionally perform a matching process (Step SB-2 inFIG. 7) of matching a movement pattern with false-positive patterns.

Specifically, the movement detecting unit 102 c evaluates whether aspecific false-positive pattern targeted for exclusion is detectedbefore and after detection of a pattern corresponding to a page turningmovement. When the movement detecting unit 102 c determines that afalse-positive pattern is detected, the movement detecting unit 102 cexcludes the detection so that a trigger for starting a read operationis not issued. FIG. 19 is a flowchart representing a subroutine of afalse-detection exclusion process.

As illustrated in FIG. 19, when the movement detecting unit 102 cdetects a page turning movement (Step SD-1), the movement detecting unit102 c determines whether there is a specific pattern corresponding to afalse-positive pattern over m frames (N-m to N+m) before and after thecurrent frame (N) and the next frame (N+1) in which a page turningmovement is detected (Step SD-2). Then, when the movement detecting unit102 c detects a false-positive pattern (No in Step SD-2), the movementdetecting unit 102 c returns the process to Step SD-1 and monitors for anew page turning movement. In contrast, when the movement detecting unit102 c determines that movement patterns are not a false-positive pattern(Yes in Step SD-2), the read-start determining unit 102 d issues atrigger for starting a read operation (Step SD-3) and the linear-imageobtaining unit 102 e obtains a scanned image (Step SD-4).

As an example of a false detection, if a movement pattern corresponds toat least one of (1) a case where a movement is detected in all regions,(2) a case where a specific region did not move, and (3) a case where amovement is detected at a point that does not move during a page turningmovement, the movement detecting unit 102 c may exclude the detection asa false-positive pattern. FIG. 20 is a diagram illustrating an exampleof a detection of changed blocks in (1) a case where a movement isdetected in all regions.

As illustrated in FIG. 20, when a movement is detected in all regions atthe same time, it is considered that the whole book is moved in thedetection range of the area sensor. Thus, when changed blocks aredetected in all of the Left area, the Center area, and the Right area,the movement detecting unit 102 c detects it as a false-positive patternand excludes the detection so that a read operation is not started. FIG.21 is a diagram illustrating an example of the detection of changedblocks in (2) a case where a specific region did not move.

When a page of a book is turned, the page passes over the central regionof the book and therefore the central region moves by necessity.However, when a specific region that is to move in a page turningmovement does not move, it is considered that the page was not turnedbut a hand or the like moved. Accordingly, as illustrated in FIG. 21,when only part of the Center area moves and the specific region MA-1does not move, the movement detecting unit 102 c determines that themovement pattern is a false-positive pattern and excludes the detection.FIG. 22 is a diagram illustrating an example of the detection of changedblocks in (3) a case where a movement is detected at a point that doesnot move during a page turning movement.

As illustrated in FIG. 22, when only a page of a book is turned, amovement is not normally detected in the region MA-2 because the regionMA-2 is away from the region in which the book is placed. In this case,it is considered that a page was not turned but a hand or the likemoved. Therefore, it is highly likely that a region that is not relatedto the movement of the target medium moves and the movement is falselydetected. Thus, a read operation is not started. When the specificregion MA-2 moves, the movement detecting unit 102 c determines that themovement pattern is a false-positive pattern and excludes the detection.Movements may be classified by creating such a specific point.

Here, the description refers back to FIG. 7. After the overhead scanner100 performs a detection process SB-1 of detecting a page turningmovement and a false-detection exclusion process SB-2, the overheadscanner 100 may perform a hand-removal monitoring process SB-3 beforeperforming a scanned-image obtaining process SB-4. In other words, theread-start determining unit 102 d may determine that a read operation bestarted on the condition that the movement based on the movement patterncalculated by image difference extraction has stopped. FIG. 23 is aflowchart representing a subroutine of a hand-removal monitoringprocess.

As illustrated in FIG. 23, when the detection of a page turning movementdescribed above is not excluded as a false detection and a trigger forstarting a read operation is issued (Step SE-1), the read-startdetermining unit 102 d determines whether there is a change in thedifference image between the image of the current frame (N) and theimage of the last frame (N−1) calculated by the movement-patterncalculating unit 102 b (Step SE-2). When there is a change in thedifference image (No in Step SE-2), the read-start determining unit 102d returns the process to Step SE-1 and stops the start of a readoperation. In contrast, when there is no change in the difference image(Yes in Step SE-2), the read-start determining unit 102 d determinesthat a read operation be started and the linear-image obtaining unit 102e obtains a scanned image (Step SE-3). FIG. 24 is a diagramschematically illustrating an example of an extracted image when a handremains in place.

It is preferable not to start a read operation until the movement ofremoving a hand from the region is completed or the movement of pressinga page of a book and holding the page in place is completed after thepage of the book is turned. Therefore, as illustrated in FIG. 24, whilea changed block continues to be detected, the read-start determiningunit 102 d stops the read start process and waits for the start of aread operation. Then, after a predetermined number of seconds from whenit is recognized that there is no change in the image due to themovement of removing a hand or holding a page of a book, the read-startdetermining unit 102 d may determine that a read operation be started.

Here, the description refers back to FIG. 7. The linear-image obtainingunit 102 e obtains image data of linear images from the linear sensor 13by controlling the linear imaging unit 110 in accordance with thetrigger for starting a read operation issued by the read-startdetermining unit 102 d (Step SB-4).

Then, the control unit 102 of the overhead scanner 100 performs an imagecorrection process (Step SB-5). For example, the control unit 102 maydivide the linear images obtained by the linear-image obtaining unit 102e along a page boundary and correct the images so that warpage of paperof the opened page is eliminated. Moreover, the control unit 102 maydetect a skin-color portion region from an image using a known patternrecognition algorithm or the like and correct it to white or the like onthe basis of the color (skin color) of a user's hand stored in theindicator file 106 c.

Then, the control unit 102 of the overhead scanner 100 stores image dataof the corrected image in the processed-image data file 106 b (StepSB-6) and ends the process.

The above is an example of the embodying process performed by theoverhead scanner 100 in the present embodiment. In the embodying processdescribed above, an explanation is given of the flow of a single processin a case where images in a horizontal double-page spread are read;however, it is possible to automatically continue to read otherdouble-page spreads by repeating the processes in Step SB-1 to Step SB-5described above.

3. Summary of Present Embodiment and Other Embodiments

As described above, according to the present embodiment, the overheadscanner 100 successively obtains area images by controlling the areaimaging unit 120, calculates a movement pattern by image differenceextraction by using the area images, and detects a page turning movementon the basis of the calculated movement pattern. When a page turningmovement is detected, the overhead scanner 100 determines that a readoperation by the linear sensor 13 be started. Consequently, it ispossible to prevent a false detection and detect the start of a readoperation with high accuracy.

More specifically, with a conventional method of determining a pageturning movement on the basis of velocity vectors of feature points,vectors can be detected only near the central portion where the amountof movement of feature points is large and a fine classification processcannot be performed. According to the present embodiment, even when themovement of a feature point that moves slowly cannot be recognized as arelevant velocity vector, the slow movement can be detected by imagedifference extraction.

Moreover, when an extremely white medium is placed in the area sensorrange, the feature points become weak and, when a small medium, such asA6 paper, is placed, the number of feature points decreases. Therefore,conventionally, velocity vectors are difficult to calculate on the basisof the feature points and thus detection is not accurately performed.According to the present embodiment, for example, even when the featurepoints are weak due to a white medium or even when the number of featurepoints is small due to a small medium, it is possible to detect themovement of shadows and fine movement, which are not conventionallydetected, by extracting a difference in an image. Thus, the movement ofan object can be detected without depending on the medium.

Moreover, if the edge of the medium is not clear, conventionally, thefeature points are not successfully detected. Accordingly, an areasensor is required to have a certain level of resolution; therefore, anexpensive and highly accurate sensor needs to be used. According to thepresent embodiment, even if the resolution of an area sensor is reduced,a movement can be detected as long as a difference in an image can beobtained. Thus, the apparatus can be configured with a less expensivesensor.

Moreover, in an example of a conventional technology, the movement andposition with and at which a large velocity vector is obtained arelimited; therefore, there is a limit in narrowing down themovement-detection determination condition and reducing falsedetections. For example, vectors with which a page turning movement canbe detected are often limited to large vectors obtained when theposition of a page is 60° to 120° with respect to the horizontal plane.According to the present embodiment, because the initial and finalmovements during page turning are definitely detected due to the certainamount of difference in an image in the end portions of the screen, evenwhen the position of a page is not 60° to 120° with respect to thehorizontal plane, a page turning movement can be accurately detected.

Moreover, in an example of a conventional technology in which aprojection pattern is projected, the projection pattern becomes unevenfrom the beginning in a region other than a flat surface; therefore, theoperation cannot be performed successfully in some cases. However,according to the present embodiment, the operation can be performedsuccessfully irrespective of the unevenness of the detection region.Moreover, it is possible to detect a special pattern, such as themovement of a hand and the movement of a book, in a region that cannotbe detected on the basis of only the transition of the movement of areflected projection pattern. Moreover, even if a medium is thin or aregion to be detected is not flat, a page turning movement can bedetected by detecting the transition of the movement of a page.

Moreover, according to the present embodiment, the overhead scanner 100obtains an infrared image by infrared irradiation by using thearea-image obtaining unit 102 a. In the present embodiment, infraredrays are emitted to a detection region. This is different from anexample of a conventional technology in which a projection pattern isused. Therefore, the transition of the movement in the region and themovement of an object can be clearly detected.

Moreover, according to the present embodiment, the overhead scanner 100screens out false-positive patterns other than a page turning movementand excludes the detection by using the movement detecting unit 102 c.Therefore, even when the movement pattern accidentally corresponding toa page turning movement is detected, a falsely detected movement patternis excluded. Accordingly, the determination process of a page turningmovement can be improved.

Moreover, according to the present embodiment, the overhead scanner 100determines that a read operation be started by the read-startdetermining unit 102 d on the condition that the movement based on themovement pattern calculated by image difference extraction has stopped.Therefore, when a page is moving or a hand is moving, a read operationis kept on standby. Accordingly, a clear image of a stationary objectcan be obtained.

Moreover, according to the present embodiment, the overhead scanner 100divides an image region into a predetermined number of blocks andcalculates a movement pattern by using the movement-pattern calculatingunit 102 b; therefore, the overhead scanner 100 determines a change foreach block and thus the processing speed can be improved.

Moreover, according to the present embodiment, the overhead scanner 100divides an image region into an arbitrary number of blocks and, when thenumber of changed pixels in one block is equal to or greater than apredetermined value, evaluates the block as a changed block, by usingthe movement-pattern calculating unit 102 b. Therefore, the processingon the basis of the number of changed pixels can be speeded up.

Moreover, according to the present embodiment, the overhead scanner 100divides an image region corresponding to the initial motion of a pageturning movement into smaller blocks by using the movement-patterncalculating unit 102 b. Accordingly, it is possible to detect morechange information on the initial movement of a page turning movement,which tends to represent the characteristics of a page turning movement,such as the movement of holding a page by the hand and the movement ofthe edge of a page, by setting the number of divisions to be large inboth end portions of the page.

Moreover, according to the present embodiment, in the overhead scanner100, if a movement pattern corresponds to at least one of (1) a casewhere a movement is detected in all regions, (2) a case where a specificregion did not move, and (3) a case where a movement is detected at apoint that does not move during a page turning movement, the movementdetecting unit 102 c may exclude the detection as a false-positivepattern. Accordingly, (1) if a movement is detected at the same time inall the regions of an area sensor, it is considered that environmentallight may change or a medium itself may be moved, which is differentfrom the movement pattern of a page turning movement; therefore, a falsedetection can be excluded. Moreover, (2) if a movement is not detectedin a region that actually needs to move during a page turning movement,this is simply considered as the movement of a hand or the like that isnot accompanied with a page turning movement. Therefore, a falsedetection can be excluded. Moreover, (3) when a button is pressed, amovement is detected in a specific area different from an area in thecase of a page turning movement; therefore, even if a movement patternclosely resembling a page turning movement is detected before and afterthe page turning movement, a false detection can be excluded.

Furthermore, the present invention may be implemented by variousdifferent embodiments within the scope of the technical idea describedin the claims in addition to the above-described embodiments. Forexample, the infrared light source 130 may output light in a wavelengthregion other than the infrared region, and the area sensor 22 may detectlight in a wavelength region other than the infrared region. Moreover,an explanation is given of the case where the overhead scanner 100performs the processing in stand-alone mode as an example; however, theoverhead scanner 100 may perform the processing in response to a requestfrom a client terminal in a cabinet different from the overhead scanner100 and return the processing results to the client terminal. Moreover,among the processings described in the embodiments, all or part of theprocessings described as automatic processing may be performed manuallyor all or part of the processings described as manual processing may beperformed automatically by well-known methods. In addition thereto, theprocessing procedures, the control procedures, the specific names, theinformation including registered data of each processing, the screenexamples, and the database configurations, described in the literaturesand drawings above may be arbitrarily modified unless otherwiseindicated.

Furthermore, each component of the overhead scanner 100 illustrated inthe drawings is formed on the basis of functional concept, and is notnecessarily configured physically the same as those illustrated in thedrawings. For example, all or any part of the processing functions thatthe devices in the overhead scanner 100 have, and particularly eachprocessing function performed by the control unit 102, may beimplemented by a CPU (Central Processing Unit) and a program interpretedand executed by the CPU, or may be implemented as hardware by wiredlogic. The program is recorded in a recording medium, which will bedescribed later, and is mechanically read by the overhead scanner 100 asnecessary. Specifically, the storage unit 106, such as a ROM and an HDD,or the like records a computer program for executing variousprocessings. This computer program is executed by being loaded into aRAM and configures the control unit in cooperation with the CPU.Moreover, this computer program may be stored in an application programserver that is connected to the overhead scanner 100 via an arbitrarynetwork, and all or part thereof may be downloaded as necessary.

Furthermore, the program according to the present invention may bestored in a computer-readable recording medium or may be configured as aprogram product. The “recording medium” includes any “portable physicalmedium”, such as a memory card, a USB memory, an SD card, a flexibledisk, a magneto-optical disk, a ROM, an EPROM, an EEPROM, a CD-ROM, anMO, a DVD, and a Blue-ray Disc. Moreover, the “program” refers to a dataprocessing method written in any language and any description method andis not limited to a specific format, such as source codes and binarycodes. The “program” is not necessarily configured unitarily andincludes a program constituted in a dispersed manner as a plurality ofmodules and libraries and a program that implements its functions incooperation with a different program representative of which is an OS(Operating System). Well-known configurations and procedures can be usedfor the specific configuration and reading procedure for reading arecording medium, the installation procedure after reading a recordingmedium, and the like in each device illustrated in the presentembodiment.

Various databases and the like (the image-data temporary file 106 a, theprocessed-image data file 106 b, and the indicator file 106 c) stored inthe storage unit 106 are a storage unit, examples of which is a memorydevice, such as a RAM and a ROM, a fixed disk drive, such as a harddisk, a flexible disk, and an optical disk, and stores various programs,tables, databases, and the like that are used for various processings.

Moreover, the overhead scanner 100 may be configured as an informationprocessing apparatus, such as well-known personal computer andworkstation, or may be configured by connecting an arbitrary peripheraldevice to the information processing apparatus. Moreover, the overheadscanner 100 may be realized by installing software (including program,data, and the like) that causes the information processing apparatus torealize the method in the present invention. A specific form ofdistribution/integration of the devices is not limited to thoseillustrated in the drawings and it can be configured such that all orpart thereof is functionally or physically distributed or integrated, byarbitrary units, depending on various additions or the like or dependingon functional load. In other words, the above-described embodiments maybe performed by arbitrarily combining them with each other or theembodiments may be selectively performed.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An overhead scanner comprising: an area sensor;and a control unit, wherein the control unit includes: an area-imageobtaining unit that successively obtains a plurality of images bycontrolling the area sensor, a movement-pattern calculating unit thatcalculates a movement pattern by image difference extraction which is toextract a difference between gradation values of pixels at the samecoordinates by using the images obtained by the area-image obtainingunit, a movement detecting unit that detects a page turning movement ona basis of the movement pattern calculated by the movement-patterncalculating unit, and a read-start determining unit that determines thata read operation be started when the page turning movement is detectedby the movement detecting unit.
 2. The overhead scanner according toclaim 1, wherein the area-image obtaining unit obtains an infrared imageby infrared irradiation.
 3. The overhead scanner according to claim 1,wherein the movement detecting unit screens out a false-positive patternother than the page turning movement and excludes a detection of thefalse-positive pattern.
 4. The overhead scanner according to claim 1,wherein the read-start determining unit determines that a read operationbe started on a condition that a movement on a basis of the movementpattern calculated by the image difference extraction has stopped. 5.The overhead scanner according to claim 1, wherein the movement-patterncalculating unit divides an image region into a predetermined number ofblocks and calculates the movement pattern.
 6. The overhead scanneraccording to claim 5, wherein the movement-pattern calculating unitdivides an image region into an arbitrary number of blocks and, whennumber of changed pixels in one block is equal to or greater than apredetermined value, evaluates the block as a changed block.
 7. Theoverhead scanner according to claim 5, wherein the movement-patterncalculating unit divides an image region corresponding to an initialmovement of the page turning movement into smaller blocks.
 8. Theoverhead scanner according to claim 3, wherein when a movement patterncorresponds to at least any one of a case where a movement is detectedin all regions, a case where a specific region did not move, and a casewhere a movement is detected at a point that does not move during pageturning, the movement detecting unit excludes a detection as thefalse-positive pattern.
 9. An image obtaining method comprising: anarea-image obtaining step of successively obtaining a plurality ofimages by controlling an area sensor; a movement-pattern calculatingstep of calculating a movement pattern by image difference extractionwhich is to extract a difference between gradation values of pixels atthe same coordinates by using the images obtained in the area-imageobtaining step; a movement detecting step of detecting a page turningmovement on a basis of the movement pattern calculated in themovement-pattern calculating step; and a read-start determining step ofdetermining that a read operation be started when the page turningmovement is detected in the movement detecting step, wherein thearea-image obtaining step, the movement-pattern calculating step, themovement detecting step, and the read-start determining step areexecuted by a control unit of an overhead scanner that includes the areasensor and the control unit.
 10. A non-transitory computer-readablerecording medium that stores therein a program that causes a controlunit of an overhead scanner including an area sensor and the controlunit to execute: an area-image obtaining step of successively obtaininga plurality of images by controlling the area sensor; a movement-patterncalculating step of calculating a movement pattern by image differenceextraction which is to extract a difference between gradation values ofpixels at the same coordinates by using the images obtained in thearea-image obtaining step; a movement detecting step of detecting a pageturning movement on a basis of the movement pattern calculated in themovement-pattern calculating step; and a read-start determining step ofdetermining that a read operation be started when the page turningmovement is detected in the movement detecting step.
 11. The imageobtaining method according to claim 9, wherein in the movement-patterncalculating step, an image region is divided into a predetermined numberof blocks and calculates the movement pattern.
 12. The image obtainingmethod according to claim 11, wherein in the movement-patterncalculating step, an image region is divided into an arbitrary number ofblocks and, when number of changed pixels in one block is equal to orgreater than a predetermined value, the block is evaluated as a changedblock.
 13. The image obtaining method according to claim 11, wherein inthe movement-pattern calculating step, an image region is dividedcorresponding to an initial movement of the page turning movement intosmaller blocks.
 14. The image obtaining method according to claim 9,wherein in the movement detecting unit, a false-positive pattern otherthan the page turning movement is screened out and a detection of thefalse-positive pattern is excluded.
 15. The image obtaining methodaccording to claim 14, wherein when a movement pattern corresponds to atleast any one of a case where a movement is detected in all regions, acase where a specific region did not move, and a case where a movementis detected at a point that does not move during page turning, adetection is excluded as the false-positive pattern in the movementdetecting step.
 16. The non-transitory computer-readable recordingmedium according to claim 10, wherein in the movement-patterncalculating step, an image region is divided into a predetermined numberof blocks and calculates the movement pattern.
 17. The non-transitorycomputer-readable recording medium according to claim 16, wherein in themovement-pattern calculating step, an image region is divided into anarbitrary number of blocks and, when number of changed pixels in oneblock is equal to or greater than a predetermined value, the block isevaluated as a changed block.
 18. The non-transitory computer-readablerecording medium according to claim 16, wherein in the movement-patterncalculating step, an image region is divided corresponding to an initialmovement of the page turning movement into smaller blocks.
 19. Thenon-transitory computer-readable recording medium according to claim 10,wherein in the movement detecting unit, a false-positive pattern otherthan the page turning movement is screened out and a detection of thefalse-positive pattern is excluded.
 20. The non-transitorycomputer-readable recording medium according to claim 19, wherein when amovement pattern corresponds to at least any one of a case where amovement is detected in all regions, a case where a specific region didnot move, and a case where a movement is detected at a point that doesnot move during page turning, a detection is excluded as thefalse-positive pattern in the movement detecting step.